Pleural and extrapleural solitary fibrous tumor:clinical and pathological analysis

Objective To review the clinicopathological characteristics,differential diagnosis,treatment and prognosis of pleural and extrapleural solitary fibrous tumor(SFT) .Methods Tissue sections from 6 cases of pleural SFT and 8 cases of extrapleural SFT were examined by light microscopy and immunohistochemistry.Results Histologically,the lesions were composed of a varying admixture of spindle-shaped to round cells,variably collagenous stroma and branched hemangiopericytoma-like vessels.Eleven cases were characterized by alternating hypercellular and hypocellular areas,2 cases had moderate to high cellularity and little intervening fibrosis;1 case presented the combination of the two growth patterns with multiple masses.Immunohistochemically,all cases were positive for CD34,bcl-2 and CD99,and negative for desmin,S-100,EMA,CK(AE1/AE3) and p53.Two cases were focally and weakly positive for SMA.Two cases recurred,including 1 case of recurring malignant SFT with multiple masses attached to the visceral and parietal pleura.Conclusion Extrapleural SFT shares the clinical,pathologic and immunohistochemiacal features with pleural SFT.SFT shows a wide spectrum of histological features and has several variants.The tumor cells are diffusely or focally positive for CD34,bcl-2 and CD99,which may be of value for pathologic and differential diagnosis.